1. Field of the Invention
The present invention relates generally to the agricultural field, and more specifically to mobile irrigation systems in which a suspended irrigation pipe is carried over a field in a circular or lateral linear path to irrigate the underlying crops. The present invention is a track driven support tower for such suspended irrigation pipes or lines, which reduces crop damage by means of its narrow track and width and further reduces field damage by means of the large area of the elongate track which spreads the load of the tower and pipe over a larger surface area.
2. Description of Related Art
The development of mobile irrigation systems has opened up large areas of land which would otherwise be too arid for growing certain crops which require larger amounts of water. These systems comprise a relatively long irrigation pipe or line suspended over the crops by a series of mobile towers, which carry the line in a linear or circular path to irrigate the underlying crops.
While such irrigation systems have provided great benefit to large farming operations by allowing them to grow more profitable crops and/or to produce greater yields per acre, such systems are not without their drawbacks. Most conventional mobile irrigation systems use two or more wheels and tires to support the pipe tower(s), rather than a track system as in the present invention. While such wheeled systems function adequately to provide motion for the tower and to carry the overlying irrigation pipe or line, the considerable weight of the overlying irrigation pipe and the water therein (which may comprise a run of over one hundred feet) results in a considerable load on the wheels and tires of the support tower(s). This often results in the wheels and tires forming deep ruts in the underlying surface, particularly when that surface has been softened by irrigation.
These ruts and tracks then interfere with other machinery (harvesters, etc.) operated in the field subsequent to the irrigation operations. In some cases, the tracks and ruts produced by the irrigation equipment can be so large or deep that other types of equipment are damaged by repeated use over such areas. Moreover, the production of such ruts and tracks leads to water collection in the ruts and uneven irrigation of the crops in the fields, as well as wasted water which collects within the ruts. Such deep ruts and tracks have also been known to cause the wheels of the irrigation towers to become stuck during later passage through the same area or track, particularly if the track has been filled with water and the ground is excessively soft as a result.
Another problem with conventional wheeled mobile irrigation towers is crop damage due to the relatively wide wheel and tire necessary to support the heavy weight of the overlying irrigation pipe and support tower. For example, a pipe having an internal diameter of only six inches and a span of one hundred feet would carry on the order of 150 gallons of water weighing about 1200 pounds. When the weight of the pipe, its support structure, the support towers, and mobile structure (wheels, propulsion motor(s), etc.) are added to the weight of the water, it will be seen that each tower must support a considerable load. Hence, most such towers utilize relatively large diameter and wide tires in an attempt to distribute the load over a relatively wide area. This results in a relatively large percentage of the crop being knocked down or damaged, due to the passage of the wide wheel, tire, and other tower structure thereover.
While track driven mobile irrigation systems have been developed in the past in an attempt to overcome at least the problem of the system becoming mired in its own ruts or tracks, as well as to spread the weight of the apparatus over a relatively large area, such prior art systems do nothing to provide the narrowest possible track width in order to reduce damage to crops to the greatest possible extent. While it may seem obvious to reduce the width of the tower structure which passes through the crops, this has not been accomplished to the maximum possible degree in any of the devices of the prior art of which the present inventor is aware.
Accordingly, a need will be seen for a track drive for a mobile irrigation system which provides a relatively narrow track and drive system width in order to reduce damage to crops to the greatest extent possible, but which track is relatively long in order to provide the greatest practicable contact area for the track and hence the lowest possible unit pressure for the overlying structure. The present track drive accomplishes this by means of a single, central drive wheel and a pair of outlying support wheels disposed to each end of the track length to provide a relatively long track span or length. Intermediate track support may be provided by additional idler wheels between the central drive wheel and outlying support wheels, if so desired. The single drive wheel precludes need for drive shafts extending alongside the device to provide motive force for plural wheels, thus reducing the overall width of the assembly. The drive wheel is also dished to provide an interior volume which houses the drive motor and gearbox for the assembly, again greatly reducing the overall width of the assembly.
The present track drive system also includes an independent suspension system for the central drive wheel and outlying wheels, allowing the device to traverse uneven ground while still maintaining maximum contact with the underlying surface to spread the system load and maintain traction. The single, larger diameter central drive wheel is in contact with both the upper and lower track segment at all times, in order to produce continuous drive force to the track.
A discussion of the related art of which the present inventor is aware, and its differences and distinctions from the present invention, are discussed below.
U.S. Pat. No. 1,541,026 issued on Jun. 9, 1925 to Arthur R. Blewett, titled xe2x80x9cTractor Machine,xe2x80x9d describes an endless track and wheel assembly having a single, central sprocketed drive wheel with forward and rearward non-driven wheels. The central drive wheel contacts the track tangent to both its lowermost and uppermost portions of its rim, thus simultaneously driving the track from both its lower and upper peripheries. However, the Blewett track and wheel assembly differs from the present track drive system in several respects. First, it is noted that all three wheels are linked together by a common structure, thus preventing any relative motion between wheels for traversing uneven surfaces more smoothly. Second, the track is considerably wider than the wheels, as would be necessary to spread the load over a relatively large area in view of the short length of the assembly (all three wheels are spaced apart by only a small fraction of their diameters). It is also noted that Blewett does not provide any means of supporting an overlying structure with his track and wheel assembly.
U.S. Pat. No. 1,613,598 issued on Jan. 11, 1927 to Edward R. Armstrong, titled xe2x80x9cTraction Appliance For Automobiles,xe2x80x9d describes an assembly adapted for installation on an automobile or the like. The assembly includes a specially modified wheel with a solid tire having a series of transverse slots, with a rigid frame including a pair of opposed track end wheels and a track passing around the end wheels and central main wheel. The track engages the transverse slots of the main wheel to drive the vehicle. The structure is thus generally like the structure of the Blewett ""026 U.S. patent discussed immediately above, with the rigid structure failing to provide relative articulation between the wheels to better accommodate surface irregularities. As in the Blewett ""026 apparatus, Armstrong makes no provision for supporting any overlying structure, as the sole attachment to the vehicle is by means of the drive axle to which the wheel is attached.
U.S. Pat. No. 1,966,783 issued on Jul. 17, 1934 to Maurice A. Balaam, titled xe2x80x9cPortable Overhead Irrigation Plant,xe2x80x9d describes an automatically propelled mobile irrigation device having a track drive in at least one embodiment. The Balaam device differs from the present invention in several respects. First, the track of the track drive embodiment is considerably wider than the present relatively long and narrow track, as is clearly shown in FIG. 5 of the Balaam U.S. patent. This would result in considerably more crop damage along the path of the Balaam device than would occur with the present invention, which when considering that the track path extends at least completely across the field for lateral irrigation systems, and much longer for circular systems, results in considerable crop damage by the Balaam device. Secondly, the Balaam tracked device has a central water powered motor driving forwardly and rearwardly disposed drive wheels. As in the other devices discussed above, the Balaam device also uses a rigid frame which does not provide any relative articulation between wheels.
U.S. Pat. No. 2,711,615 issued on Jun. 28, 1955 to Nelson R. Boice, Jr., titled xe2x80x9cApparatus For Processing Surface Areas,xe2x80x9d describes a mobile irrigation system with the pipe supported by a series of track drive devices. The Boice, Jr. drive apparatus is more closely related to that of the Balaam ""783 U.S. patent discussed immediately above than to the present invention, in that Boice, Jr. provides a single forwardly disposed drive wheel driven by a centrally located motor. A series of idler or bogie wheels is positioned between the forward rearward wheels in the track assembly. All wheels of the Boice, Jr. assembly are installed on a rigid framework which does not allow articulation of the wheels, as does the independent suspension system of the present machine.
U.S. Pat. No. 2,931,579 issued on Apr. 5, 1960 to Clarence W. Ruddell, titled xe2x80x9cAutomatic Irrigation System,xe2x80x9d describes a linear mobile irrigation system having a track drive device and a series of non-driven tracked supports disposed along the length of the pipe. The track drive assembly comprises two widely spaced narrow tracks extending laterally from a single carriage which supports the irrigation pipe. The relatively wide carriage is so low that it would damage almost any crop over which it passed, thus causing significant crop damage. The drive system comprises an offset motor which drives an upper intermediate wheel, with the track passing around the intermediate wheel and the two track wheels to drive all of the wheels. As in the case of other devices discussed above, the Ruddell device also has a rigid frame precluding articulation and independent movement of the wheels.
U.S. Pat. No. 4,365,748 issued on Dec. 28, 1982 to Robert R. Emrich, titled xe2x80x9cSelf-Driven Mobile Center Pivot Irrigation System,xe2x80x9d describes a system having a mobile tractor device for transporting the system and for serving as the central pivot of the system for its operation. One or more radially outlying propulsion devices are also provided, which more closely relate to the present invention. However, the outlying propulsion devices still differ considerably from the present track drive system in that they have two wheels, each of which is driven by a separate independent belt which wraps about the circumference of its respective wheel. The two belts are in turn driven by a single central gearbox powered by a water driven motor. The motor and gear reduction are offset considerably from the plane of the wheels, unlike the present system. Also, while each wheel has a separate brace structure, the two braces are rigidly secured together during operation to preclude relative wheel movement.
U.S. Pat. No. 4,452,394 issued on Jun. 5, 1984 to Robert R. Emrich, titled xe2x80x9cSelf Propelled Irrigation Systems,xe2x80x9d describes various embodiments of such a system. One embodiment comprises a pair of wheels driven by a common belt and drive motor positioned between the wheels. This device is more closely related to the device of the ""748 U.S. patent to the same inventor discussed immediately above, than to the present invention. The two wheels of the Emrich ""394 device are rigidly affixed relative to one another by the frame structure, unlike the present track drive system with its articulated independent suspension for the wheels.
U.S. Pat. No. 5,078,326 issued on Jan. 7, 1992 to Hubbart L. Wright, titled xe2x80x9cMobile Irrigation Equipment Belt Traction Apparatus,xe2x80x9d describes a system having a series of four wheels, with a single belt extending therearound. At least one of the front and rear wheels is driven by a motor at the hub thereof. The motor(s) and support structure for the tower supported above the wheels, is laterally offset from the plane of the wheels, rather than having the wheels located symmetrically beneath the tower structure as in the present invention. The asymmetric relationship between the wheels and tower, place a significant bending load upon the wheel axles and lower tower components, requiring a significantly heavier structure than that of the present invention. Moreover, the entire wheel support frame of the Wright apparatus is a single rigid structure, with no relative movement of the wheels permitted. While Wright clearly recognizes the problems associated with wheeled mobile irrigation systems, as indicated in his discussion in the Background of the Invention of his U.S. patent, his invention falls short of the solution provided by the present invention.
U.S. Pat. No. 6,131,833 issued on Oct. 17, 2000 to John A. Chapman, titled xe2x80x9cTracked Drive Tower For A Self-Propelled Irrigation System,xe2x80x9d describes a track drive system having a single forwardly disposed drive wheel and a series of trailing bogie or idler wheels within the track run, with each pair of idler wheels mounted to a beam which is in turn pivotally attached to a single, rigid overlying structure. The only articulation provided is by means of each pair of idler wheels rocking about its common attachment shaft. Chapman does not provide any spring suspension means, nor adjustment means for such a suspension, in his apparatus. Moreover, no central drive wheel is provided, as is the case of the present invention. It is also noted that the drive motor and gear reduction drive are disposed well outside the plane of the wheels and track, unlike the present invention. Such an installation results in an even wider path for the track assembly as it traverses a field, with the motor and gear reduction damaging additional crops due to their relatively low placement and axial extension from the plane of the wheel and track.
Australian Patent Publication No. 227,737 published on Aug. 27, 1959 to Machinery Specialties Pty. Limited, titled xe2x80x9cMobile Irrigation Sprayer,xe2x80x9d describes an apparatus having a series of drive towers disposed along a length of pipe. Each drive tower comprises a forward, an intermediate, and a rearward wheel, with a track extending around the three wheels. Only the forward wheel is driven by a linear water motor, which alternately extends and retracts a strut which in turn drives a ratchet arrangement on the front wheel; the drive mechanism thus resembles that of the Balaam ""783 U.S. patent, discussed further above. As in the other devices known to the present inventor and discussed above, the Machinery Specialties system has a rigid, unitary frame precluding any movement of the wheels relative to one another for more effective travel over uneven terrain, as provided by the present invention.
Australian Patent Publication No. 291,021 published on Jul. 13, 1967 to Machinery Specialties Pty. Limited, titled xe2x80x9cMobile Irrigation Sprayer,xe2x80x9d describes a modification of the sprayer device of the Australian ""737 Patent Publication noted immediately above. The ""021 Australian Publication describes a similar track assembly, but the ""021 assembly includes a pair of idler wheels disposed between the front and rear wheels of the track, rather than only a single idler wheel. Moreover, the ""021 assembly is driven by a conventional electric motor, rather than a linear hydraulic strut motor. Many of the same problems noted further above are evident in the device of the ""021 Australian Publication, e.g. the axially extending motor and gearbox which increase the width of crop damage area as the track passes through the crops, and the rigid frame precluding any relative suspension movement between track wheels.
Finally, Australian Patent Publication No. 293,781 published on Jul. 13, 1967 to Machinery Specialties Pty. Limited, titled xe2x80x9cMobile Irrigation Sprayer,xe2x80x9d describes a tracked apparatus having only single forward and rearward wheels within a track. Drive is provided by a hydraulic (water) cylinder motor, driving a ratchet mechanism to the rear wheel. The frame is a rigid, unitary construction, precluding any relative suspension movement of the wheels. The apparatus of the ""781 Australian Patent Publication is thus more closely related to the device of the ""737 Australian Publication to the same applicant, than to the present invention.
None of the above inventions and patents, either singly or in combination, is seen to describe the instant invention as claimed.
The present invention is a track drive apparatus particularly configured for use in driving a center pivot (circular) or linear movement mobile irrigation system. The present track drive provides numerous benefits over earlier systems of the related art, by combining a relatively narrow track and other structure to reduce crop damage with a relatively long track to provide the desired low pressure footprint for the device, to reduce rut formation and other field damage.
The present track drive includes a single central drive wheel with opposed first and second end guide wheels which guide the track around the ends of the machine. The central drive wheel has a considerably larger diameter than the two end guide wheels, thus bearing against the track along both its upper and lower peripheral areas to provide positive drive to the track at all times. The present mechanism is also articulated, to allow the two end guide wheels to move upwardly and downwardly independently of one another and relative to the central drive wheel. This allows the track drive to ride smoothly over uneven contours in the field, avoiding or at least greatly reducing any rocking action over ridges or bridging of depressions, which would tend to place the entire weight supported by the track on either one or two relatively short areas of track and reduce traction accordingly.
The track itself, as well as the associated componentry, is relatively narrow, in order to avoid lateral damage to crops to either side of the tower insofar as possible. The narrow span of the track is accomplished by providing a dished center to the central drive wheel, and placing the motor and gearbox entirely within this dished center. Thus, the motor and gearbox do not extend laterally from the remainder of the structure, as is the case with most other track configurations.
Accordingly, it is a principal object of the invention to provide a track drive for a mobile irrigation system, for use with both circular and linear movement irrigation systems for reducing crop and field damage where used.
It is another object of the invention to provide such a track drive having a single central drive wheel with opposed first and second end guide wheels, with the single central drive wheel having a diameter larger than the guide wheels for contacting both the upper and lower sides of the track surrounding the wheels simultaneously.
It is a further object of the invention to provide such track drive wherein the track and associated structure is relatively narrow to reduce lateral damage to crops as the track passes therethrough, with the single drive motor and gearbox being installed within the deeply dished center of the drive wheel and contained completely therein.
Still another object of the invention is to provide such a track drive wherein each of the wheels is independently suspended relative to the other wheels, thereby allowing the track to conform to ridges and depressions in the underlying surface and reducing bridging of depressions and rocking over ridges in the field.
It is an object of the invention to provide improved elements and arrangements thereof in an apparatus for the purposes described which is inexpensive, dependable and fully effective in accomplishing its intended purposes.
These and other objects of the present invention will become apparent upon review of the following specification and drawings.